Selective signaling system



Sept. 24, 1946. DAVIS 2,408,299

' I SELECTIVE SIGNALING SYSTEM Filed NOV. 18, 1944 Statwn ,5 Station 6Paul .Bridg Ring Statwn 2 Mart mll'p Station 4 -.Hv't 1/mTip INVENTOI ZBY t ' ATTORNEY Patented Sept. 24, 1946 UNITED STATES PATENT OFFICE- vSELECTIVE SIGNALING SYSTEMT Rowland'Fenner Davis, Tuckahoe, N..Y.,assignor to American Telephone and Telegraph Com-- pany, a corporation.of New York. Application November. 18, 1944, Serial No. 564,127

This invention relatesto selective systems and more particularly toarrangements for causing the selective operation of electro-responsivedevices such, for example, as telephone ringers on.

a multi party telephone line.

One of the systems utilized in the past to accomplish selectivesignaling on multi-party telephone lines has utilized two stationsconnected between the ti side of the line and ground and two stationsconnectedbetween the ring side of the line and ground. The stationsconnected to the tip side of the line would be oppositely poled and onewould operate when negative pulsating current was applied to the tip andthe other would operate when positive pulsating current was ap-' pliedto the tip. In like manner the two stations connected to the ring sideof the line would be oppositely poled and one would" operate whennegative pulsating current was applied to the ring and the other wouldoperate when positive pulsat ing current was appliedto the ring; Such asystem provides means for selectively signaling'four stations. Thearrangements of th'ein'ventionprovidemeans whereby additional stationsmay be added to such asystemandthese additional stations may alsobeselectively signaled without-interference to or from the'previouslymentioned stations. In one embodiment of the invention this isaccomplished by. bridging oppositely poled stations across the linezandproviding means at the central ofiice for preventing: the signalingcurrents normally used for operating theoriginal four stations fromaffecting th'ebridged: stations. Also the bridged stations are soconnectedthat the signaling currents 1 applied to selectively peratethem willnot affect the original four stations. Other. objects andfeaturesof theinven- 'tion will appear more fully. from the detaileddescription thereof hereinafter given.

The invention may be more fully understood from the followingdescription, together withthe accompanying drawing, in the figure ofwhich is shown a circuit;- diagramillustrating a; preferred Theconnections of'these tubes are such-that-thestations land 2-areoppositely poled. connected between the ring side of the line and groundwould be the signal responsive arrangements of stations 3 and 4. Theseeach include the ringers such as 12 and I4 connected to the ring side ofthe line through the gas-filled tubes II and I3.

I 4 Claims. (Cl. 179-46) 7 The connections ofthe; gas-filled tubesaresuch that the ringers are oppositely poled. Bridged across the line areshown the signal responsive means of stations 5 and 6. Each of theseincludes a ringer such as the ringers I6 and 18. These ringers arebridged across the line by means of the gas-filled tubes l5 and I! insuch a manner that; they are oppositely poled. At the central ofli cewould be provided a plurality of switches such as S1, S2, S3, S4, S5 andS6 for selectively signaling the respectivestations 1,2, 3, 4, 5 and 6.

V Y switch S1 would be operated. This would apply negative pulsatingcurrent to the tip side of the line; This negative pulsating-current, ina manner well-known in the art, would cause-the gas-filledtube I tobreak down and operate the ringer 8. Thenegative To signal station I I,

pulsating current applied to the tip side of the be the frequency ofline, however, would not operate the ringer H], as the arrangements atstation 2 are oppositely poled with respect to those of station I. 'Inarrangements used. in the past, the operation of the switch S1 wouldapply ground to the ring side of the, line duringv the ringing period toavoid excessive noise on other cable pairs due to cross induction.However, in accordance with the arrangements' o-fthis invention theswitch S1 will connect to thering side of the lineone or more antiresonant circuits such as l9 and 20. The

anti-resonant circuit 25 would present a high impedance'at, for example;20 cycles, which mightthe pulsating current applied to the tip side ofthe line. The introduction of this impedance by the anti-resonantcircuit 20 would prevent the operation of the tubes and ringers atstations 5. and 6. Because of the unsymmetrical wave shape of thepulsating current appliedto the tip of the. line, it might be desirableto provide an additional; anti-resonant circuit such as l9 to introducesufficient impedance to,

the second harmonic of. the pulsating current which might be transmittedover the line, so that this second harmonic would not operate thegasfilled tubes l5 and If! of stations 5 and 6. It is pointed out thatas the circuits is and 20 are not anti-resonant at'the higher noisefrequencies they efiectively. ground the ring side of the line withrespect to these frequencies and hence prevent exces's'ivei noise onother cable pairs due to cross induction. To operate the signalresponsive means at station 2 the switch. S2 would be operated. This.would apply positive-pulsating current to the tip side. of'the lineand, in a manner well-known inthe art, would cause the gas-filled tube,9 to operate and cause the ringer i0 too-perate,butit.would1have no,effect. on the gas-filled tube l and ringer 8'. In.like manner, theoperation of the switch Sewould connect the antipulsating current orharmonics thereof would not operate the signal responsive apparatus atstations 5 and B. In a similar manner the operation of either the switchS3 or S4 would cause the signal responsiveapparatus at station 3 orstation 4 to operate by applying either negative pulsating current orpositive pulsating current to the ring side of the line. When switch S3is operated, the anti-resonant circuits 23 and 24 would be connected tothe tip side of the line, and when switch S4 is operated theanti-resonant circuits 25 and 26 would be connected to thetip side ofthe line to prevent the operation of the signal responsive apparatus atstations 5 and. 6. To operate the signal responsive apparatus at station5, the switch S5 would be operated. This would apply negative pulsatingcurrent out over the tip side of the line and back over the ring side ofthe line, and would cause the gasfilled tube I5 to break down andoperate the ringer IS. The gas-filled tubes utilized have a definitebreak-down voltage as, for example, of between 65 and 70 volts. Thevoltage connected to both sides of the line by the operation of switchS5 is sufiicient to operate the gas-filled tube 15. However, thisVoltage will not operate the tubes 1 and 13 because they would beconnected in series with each other and the resulting voltage appliedthereto would be too low. In like manner, the voltage applied-to bothsides of the line would not operate the gas-filled tubes 9 and l I, asthey would be connected in series with each other and I the resultantvoltage would be too low to cause them to operate. In like manner, theoperation of switch S6 would apply a positive pulsating current to bothsides of the line of sufiicient voltage to cause the tube I! to breakdown'and operate the ringer 18 at station 6. As this voltage would beapplied to tubes 1 and I 3 in series and to tubes 5 and I I in series,the resultant voltage would not be sufficient to break these tubes down.

While this invention has been disclosed as embodied in certain specificforms which are deemed desirable, it is understood that it is capable ofembodiment in many and other widely varied form-s without departing fromthe spirit of the invention as defined by the appended claims.

What is claimed is:

1. A line having a plurality of signal responsive devices connectedthereto, certain of said devices being oppositely poled with respect toeach other and operatively connected between one side of said line andground, certain of said devices being oppositely poled with respect toeach other and operatively connected between the other side of said lineand ground, certain of said devices being oppositely poled with respectto each other and operatively bridged across said line, switchingmechanism for connecting positive or negative pulsating current betweenone side of said line and ground to selectively operate any of thesignal responsive devices connected to said side of the line and meansconnected by said switching mechanism between the other side of the lineand ground for presenting sufficient impedance to said pulsating currentto prevent its operation of said devices bridged across said line.

2. A line having a plurality of signal responsive devices connectedthereto, certain of said devices being oppositely poled with respect toeach other and operatively connected between one side of said line andground, certain of said devices being oppositely poled with respect toeach other and operatively connected between the other side of said,line and ground, certain of said devices being oppositely poled withrespect to each other and operatively bridged across said line,switching mechanism for connecting positive or negative pulsatingcurrent between one side of said line and ground to selectively operateany of thesignal responsive devices connected to said side of the line,means connected by said switching mechanism between the other side' ofthe line and ground for presenting suflicient impedance to saidpulsating current to prevent its operation of said devices bridgedacross said 'line, and additional switching means for connectingpositive or negative pulsating current across said line to selectivelyoperate any of said signal responsive devices bridged across said line.

3. A line having a plurality of signal responsive devices connectedthereto, two of said devices being oppositely poled with respect to eachother and connected between one side of said line and ground, anothertwo of said devices being oppositely poled with respect to each otherand connected between the other side of said line and ground, anothertwo of said devices being oppositely poled with respect to each otherand bridged across said line, switching mechanism for connectingpositive or negative pulsating current between one side of said line andground to selectively operate either. of the signal responsive devicesconnected to said side of the line, circuits anti-resonant at thefrequency of the pulsating current and harmonics thereof, and meanscontrolled by said switching means for connecting said anti-resonantcircuits between the other side of the line and ground to prevent thepulsating current or harmonics thereof from operating said devicesbridged across said line.

4. A line having a plurality of signal responsive devices connectedthereto, tWo of said devices and operatively connected'between the otherside of said line and ground, another two of said devices beingoppositely poled with respect to each other and operatively bridgedacross said line, switching mechanism for connecting positive ornegative pulsating current between one side of said line and ground toselectively operate either of the signal responsive devices connected tosaid side of the line, means connected by said switching mechanismbetween the other side of the line and ground for presenting suificientimpedance to said pulsating current to prevent its operation of saiddevices bridged across said line, and additional switching means forconnecting positive or negative pulsating current across said line toselectively operate either of said signal responsive devices bridgedacross said line, each of said signal responsive devices including agas-filled discharge tube and a ringer connected to said linethrough itsassociated tube, the break-down voltage of each tube and the voltage ofthe pulsating current utilized being such that the application to asingle tube of the voltage of the pulsating current will cause it tooperate but the application of the voltage of the pulsating current totwo of said tubes connected in series will not cause them to operate.

ROWLAND FENNER DAVIS.

